A respiratory event, which included both airway and pulmonary problems, represented the most frequent damaging event in both surviving/disabled and dead patients. These findings were consistent with those of studies in the US [5,6] and a previous Kwon study [7] in our country. In particular, the most common specific mechanism of these events (7 of 19 respiratory damaging events, 36.8%) was related to respiratory depression due to an absolute or relative overdose of sedatives or anesthetics during monitored anesthesia care (MAC). In all of these cases, surgeons or physicians provided MAC without the help of anesthesiologists. As a result, all but one case (profound brain damage) resulted in death. According to Bhananker et al. [2], who compared 121 MAC with 1,519 general anesthesia claims, the severity of injury for MAC claims was similar to that for general anesthesia claims, with a similar proportion of death and permanent brain damage. The reality in our country is that anesthesiologists have not been in charge of most MAC cases because of extremely low (roughly one-third) medical insurance fees versus those for general anesthesia. As the actual figure is believed to be larger than those sued, the government should adjust the MAC medical insurance fee to a realistic level.

Another remarkable finding was that three cases of 19 respiratory damaging events (15.8%) were attributed to difficult intubation, all of which led to death. Kwon, the former KSA legislative director, analyzed 145 cases of expert anesthesia-related consultation referrals between 1994 and 2006 and reported that five cases were attributable to difficult intubation [8]. Thus, the occurrence of major brain damage and death from difficult intubation has not decreased despite improved monitoring, devices, and equipment, when compared with that period. These major morbidities or mortalities attributable to difficult intubation could be reduced by careful preoperative airway assessment and strict adherence to practical guidelines for the management of a difficult airway [9,10]. The last updated ASA practical guidelines for managing a difficult airway were published in 1995 [10]. In fact, Peterson et al. [11] found that difficult airway claims associated with death or brain damage during induction decreased from 62% to 35% after publication of the ASA guidelines.

The use of MAC as the technique of choice for a variety of invasive or noninvasive procedures is increasing. However, given an Anesthesiology editorial [12] published in 2006 under the title, "MAC should stand for maximum anesthesia caution, not minimal anesthesiology care," potentially serious complications in association with MAC are well-known. One closed-claims analysis [2] suggested that claims associated with MAC showed a high degree of patient injury and a liability profile similar to claims associated with general anesthesia. In that study, the most common sources of injury during MAC were severe respiratory depression, resulting in death or brain damage, associated with the drugs used for sedation. Similarly, in this analysis, seven of ten MAC cases resulted in death or profound brain damage due to respiratory depression. Damaging events of the remaining three cases were systemic toxicity due to local anesthetics used concurrently (two cases) and septicemia from infected propofol-normal saline mixing solution (one case).

Most MAC cases are for simple or superficial operations that are regularly performed in a routine fashion in relatively healthy patients (ASA I or II patients). In this analysis, all patients were classified as ASA I or II (eight patients, ASA I; two, ASA II). Moreover, propofol and midazolam, the two most commonly used drugs in MAC cases, have safer pharmacokinetics than other sedatives and anesthetics. As such, they are considered to require simple, low-risk anesthesia care. Thus, a preoperative evaluation, such as a physical examination and preoperative laboratory tests, are often omitted, and intraoperative monitoring may be easily limited. Some practitioners explain the intraoperative experience to their patients as being similar to "taking a nap at a spa" and do not wish to upset their patients or drive them away to a competitor with the used of many preoperative evaluation procedures [12].

In this analysis, no preoperative laboratory tests were performed in half of the cases. In one case, no intraoperative monitoring was used. In half of the cases, pulse oximeter was the only monitoring instrument during the entire procedure. Despite patient safety benefits offered by pulse oximetry, an in-depth examination revealed that pulse oximetry was ineffective in some cases because the practitioner did not properly apply (inappropriate alarm setting or audible pulse tone off) or observe the results during the critical period. Because a practitioner cannot continuously observe oximetric values, vigilance necessitates an audible alarm or pulse tone that changes if oxygen saturation values decline.

Following general anesthesia, MAC was the second most common anesthetic technique leading to adverse outcomes in this analysis. The injury severity of MAC cases was comparable to general anesthesia cases, with 70% and 76.2% of the MAC and general anesthesia cases causing death, respectively. Furthermore, almost all injuries due to MAC in our database review were presumed to be preventable, with the use of additional or better monitoring and effective responses to adverse occurrences. Thus, MAC providers need to be aware of the risk of serious respiratory depression, and that continuous monitoring of ventilation and oxygenation, adequate resuscitation equipment, and constant vigilance are mandatory.

The most obvious difference between the previous report of Kwon [7] and our study was a marked decrease in obstetric anesthesia-related cases. While at least 18 cases (obstetric and gynecologic anesthesia-related cases were not described individually) occurred in the field of obstetric anesthesia in the former study, obstetric anesthesia-related cases were absent in this study. In our analysis, two cases of obstetrics and gynecology department (OB/GYN) occurred during dilation and curettage and gynecologic surgery. Although the relatively short evaluation period of this study may have affected the results, they may be primarily due to a combination of a decrease in the actual occurrence of obstetric anesthesiarelated adverse events and a decrease in the number of lawsuit cases (even if the occurrence of actual cases did not decrease).

However, the most likely explanation for these results is that our country has had the lowest birthrate in the world for the last decade. During this period, the birthrate decreased from an average of 1.45 babies per woman in 1998 to 1.08 babies per woman in 2008 [13]. Another possible explanation may be the local OB/GYN clinic's growing reluctance to deliver babies. As a result, most deliveries are performed in large specialized OB/GYN hospitals, general hospitals, and university hospitals. When compared with a local OB/GYN clinic, these hospitals maintain superior faculty, equipment, and systems for patient safety, thereby reducing the occurrence of adverse events. Moreover, if anesthesia-related morbidity or mortality developed, these hospitals may have greater ability to settle out of court than a local OB/GYN clinic. In contrast to our country's results, ASA-CCP closed-claims studies [14,15] have shown that even though the proportion of obstetric claims associated with maternal death decreased from pre-1990 and 1990 or later, the overall incidences of obstetric anesthesia-related claims remained unchanged during these periods (12% vs. 13%, respectively).

As an introduction to understanding our data, several major limitations must be recognized. Most important is that we cannot derive information about the actual incidence of adverse events and total numbers of anesthesia cases in specific situations. For any given time period, we only see expert consultation referrals of anesthesia-related issues from police departments, civil or criminal courts, and district health care centers via the KMA. The vast majority of injured patients do not file claims. Thus, these inherent limitations make it impossible to provide any numeric estimates of the risk for specific clinical situations. Second, the data were collected from in a retrospective manner directly from participant, and the database only has information that the reviewers could obtain from police or prosecutor records. The incompleteness of specific detailed information regarding the sequence of events or mechanism of injury makes this analysis weaker than prospectively collected data. Third, bias should also be expected in the original medical records and other case documentations, because the preparer could not be impartial [16].

However, the usefulness of this database research is evident. Prospective clinical studies may be very expensive and ethically impossible for extremely rare and fatal events, such as anesthesia-related death. A comprehensive review of expert consultation referrals and their attached references offer an alternative and concentrated data source to examine possible causes, precipitating events, and outcomes in the field of anesthesia. The insights gained from analyzing these data will continue to provide important contributions toward ensuring patient safety.

In summary, respiratory events represented the most frequent damaging event in both surviving/disabled and dead patients. More specifically, the most common mechanism for these events was related to respiratory depression due to sedatives or anesthetics used for MAC. Almost all injuries attributable to MAC were presumed to be preventable with additional or better monitoring and providing effective responses to adverse occurrences. Thus, it can be concluded that there is room for further reductions in the occurrence of severe anesthesia-related adverse outcomes by establishing practical guidelines for MAC and ensuring strict adherence to these guidelines.